For example, high-purity silica sol is used in fields of a polishing agent for silicon wafer, a raw material such as high-purity silica gel for liquid chromatography carrier, a binder for catalyst, a raw material of special zeolite, a microfiller added to paints for electronic materials, a microfiller for polymer films, and the like.
Such high-purity silica sol is generally produced by mixing silane alkoxide such as tetramethoxysilane (TMOS), tetraethoxysilane (TEOS) or the like with water and an alkaline catalyst such as ammonia or an amine compound and subjecting it to hydrolysis and condensation polymerization (for example, see Patent Literature 1).
On the other hand, silica sol (small particle size silica sol) containing silica particles of small particle size is particularly used for final polishing of a 300 mm wafer. The silica sol can improve flatness without scratches, and further, it can be expected to have an effect of removing deposits to a substrate. Further, the small particle size silica sol can be used as the polishing agent in chemical mechanical polishing during production of a large-scale integrated circuit which is being significantly miniaturized. Furthermore, by adding the small particle size silica sol to an optical film and a molded product, it is also possible to develop high hardness and obtain a film with low haze.